Flotation of minerals



Feb'. 20, 1923. 1,446,376

W. O. vBORIHERDT FLOIATION 0F MINERALS Original Filed June 4, 1919 sheets-sheet l INVENTOR WMLQBWLMM @MKB-lm, M

ATTORNEY Feb.. 20, 1923. 1,446,376 W. O. BORCHERDT FLOTATION OF MINERALS 4Original Filed June 4, 1919' 5 sheets-sheet 2 w Hy ATTORNEYS Fab. Z, E923.. lAA

w. o. BoRcl-IERDT FLOTATION OF MINERALS Original Filed June 4, `1919 3 sheets-5heet 5 ATTORNEYS 'Patented llljeh., i923 stares WALTER O. 'BORCHERDT, OF AUSTINVLLE,

VIRGNIA, ASSKGNOR T THE NEW JERSEY lZIll' COMPNY, `0F NEW( YORK, N. Y., A CORPORATION 0E' JERSEY.

FLOTATION OF MNERALS.

.application med June 4,1919, serial No. 301,832. Renewed november 27, i922.,A

To all whom it may concern: Be it known that l, WALTER U. Bonorinnnr, acitizen of the United States, residing "at Austinvill'e, in the county of lWythe, zState of Virginia, have invented certain new and useful Improvements inA the Flotation of Minerals; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable l0 ,others skilled in the art to which it appertains to make and use the same;d

This -invention relates to improvements in the diilerential separation of minerals by dotation, and contemplates an improved method of eecting a 'diii'erential separation -or concentration by flotation of mixed ores.,

orconcentrates, containing diferent valuable mineral constituents or Species; Thus, for example, the method of the invention may be 2O advantageously employed for the production of a lead concentrate and a zinc concentrate from a mixed ore or Concentrate containing .dead and zinc suliids.

\ have discovered that in the presence ot a suitable colloid certain mineral constituents n of a mixed ore pulp can be separated therefrom by flotation while lthe separation of other mineral constituents is inhibited. Thish believe, is due to the fact that different constituents of a mixed ore pulp dit'- ter in their adsorption capacity for colloids. certain constituents havingy a greater absorption capacity than others due; perhaps, 'to

their electro positive or electro negative character, asfthe case may be, and to vsimilar factors. rllhe present invention, accordingly, involves the addition to a mixed ore pulp, substantially free of flotation-inhibitory colloidal constituents, prior to the dotation 40 treatment thereof, 'or to a mixed concentrate substantially free of flotation-inhibitory colloidal constituents, prior to the retreatment thereof by otation, of a colloidal material of a suitable character and in suilicient qua-ny tity to inhibit diiierentially the flotation ofcertain ingredients while permitting'the 'lot'ation of others l The invention. is directly applicable to a mixed ore pulp naturally so free of colloidal constituents that, if subjectedto a iotation treatment in the ordinary way, Va mixed concentrate of the valuable minerals would be obtained, containing these valuable minerals in approximately the same relative proportions to each other as in the original ore.

"fand pressure.

Experience hasdemonstrated, however,that mixed. ore pulps naturally so tree of colloidal constituents as to show no inhibition toward the flotation `of at least one of the valuable minerals therein are rare, and while mixed ore pulps containing` very small quantities of deleterious colloidal constituents are sometimes encountered in practice, I find it generally advantageous to subject the raw or crude ore pulp to a preliminary treatment for the removal of inhibitory colloidal constituents.V

'Ore pulps in which there is present only a single substance in colloidal condition occur less frequently than those in which, by the time the ore has been subjected to preliminary treatment such as grinding, there are present two or more substances in colloidal condition. Frequently, such colloidal ingredients are released progressively as the grinding or other treatment to which the ore is subjected, proceeds. In some cases these various colloidal ingredients are or' opposite `sign or by virtue of some such property are enabled to combine with one another, formfing colloidal complexes; or they mutually induce flocculation or (dei'locculation` or respond Adifferently to the agents with which they are treated. rlhus in the lead, zinc, iron-, suld ore in dolomite gangue which occurs at Austinville, Va., there is always present a certain amount of colloidal clay de- 1 iived. from the oxidized capping or from the oxidized zones or water courses occurring in the ore. body. 'l` his clay eolloid is already free` in the broken ore from the mine, and in fact, as this colloid is carried by the mine Water, it is practically impossible to obtain ore which has not been broughtinto Contact with it. v

The ore body also contains a certain amount of non-crystalline silica7 or chert, which is perhaps a colloidal silica gel; and, in places, thin layers of an ialuminous shale which appears to have been at one time a colloidal slime or mud that has become hardened orindurated by the agencies of time, heat While it is generally believed that a crystalline material cannot be converted into a truly ctolloidal state by the agency of grinding only, it is well known that such materials may become colloidal if ground and weathered; and it seems obvious that a material which has once existed as a sol, and 110 has set but not crystallized, as for example the chert or shale above mentioned, would readily resume that state under the mfluence lof grinding, in the presence of water congrinding of the chert and shale (Which l call the secondary colloids) yield more readily to treatment if the primary colloid has first been removed.

Since the clay colloid is already free in the broken mine rock, While the shale, being soft, breaks up in the preliminary operations of crushing with jaw crushers and rolls, screening, jigging, etc., and the chert, beingA extremely hard and tough only breaks up, and then to a limited extent, in the final fine grinding before the flotation operation, it is relatively easy to arrange for the partial progressive separation of' these colloidal constituents, and this is what is done.

It appears also that these colloidal constituents'do not all inhibit the flotation of the various sulfids to the same degree, and, therefore, while differential flotation may be effected by progressively decreasing the amount of the naturally occurring colloidal constituents in an ore pulp and floating in stages, it is in some cases better to remove substantially all the colloidal constituents as 'a preliminary operation and then effect diferential flotation by adding the kind and amount ofy colloid tL the pulp which is found by suitable laboratory testing to lproduce the desired inhibition of the flotation of one or more of the minerals. By so doing it is easier to secure the desired effect on the mineral the flotation of which is to bein-v hibited, Without affecting the mineral which is to be floated and the subsequent removal of the inhibitory colloid from the tailing pulp of this flotation operation is often facilitated.

The aforementioned: preliminary removal of inhibitory colloidal constituents maybe effected in any lappropriate manner, as, for example, by deflocculating anddispersing the colloidal constituents by 'means of. appropriate agents or other means, so that said colloidal constituents assume a substantially permanent state of suspension in the Water of the pulp and behave much like substances in solution, in which condition they may be removed, (with the bulk of the water of the pulp) from their association with the more granular portion of the pulp by permittingl the settling or sedimentation of the latter, and dcanting off the colloid-healing water; this action being facilitated, when desired, by agitating the pulp in the presence of the deflocculating agent or by heating or cooling the pulp by commonly understood means before Aallowing the sedimentation and decantation to take place, the latter step being conducted in tanks of the types commonly used, such as the Dori', Callow or Allen tanks, and either by overflow, displacement, or counter current decantation of the colloidbearing water, accompanied, when desired, by dilution of the pulp with .fresh Water to further facilitate the removal of the colloids. 'lhe preliminary removal of inhibitory colloidal constituents may also be effected by a preliminary flotation treatment under conditions permitting the removal by flotation of' the colloidal constituents while substantially inhibiting the flotation of the mineral particles, in which .case the colloid bearing pulp is treated in a manner similar to ordinary froth flotation, but employing for the purpose of forming and,` stabilizing the froth an agent or agents selective for colloids rather than for metall'if'erous minerals, and using froth flotation apparatus of the kind commonly employed, as for example the Cal'- low cell, whereby the colloidal constituents of' the pulp and a portion of lthe water,- together with the greater part of the froth forming agent, are removed from the pulp in the form of a colloid-bearing. froth, substantially free of valuable numerals, and leaving the granular residue of the pulp substantially free ofigcolloids. ln the case of a mixed ore pulp'` containing valuable minerals, gangue and inhibitory colloids, the raw or crude pulp. may be first treated for the removal of substantially all of the inhibitory colloids, for example, by either of the methods hereinbefore described, and the resulting pulp then subjected to a fiotation treatment with the vievvvof obtaining a mixed concentrate of the valuable minerals.

According to the present invention, there is added to the mixed ore pulp, or to the mixed concentrate, either naturally free of inhibitory colloidal constituentsor freed of Y such constituents as previously described. a small amount of a suitable colloid, either organic or inorganic, which will differentially inhibit the Vflotation of certa-in of the mineral constituents, without inhibiting or only inhibit-ing to a lesser degree the flotation of' certain other mineral constituents. The colloids Which are added will depend upon the properties of the ingredients of the ore pulp, i. e., upon the electropositive or electro-negative character of the ingredients and upon the relative att faction thereoffor the added colloids, the colloidal particles being commonly adsorbed by ingredients of opposite polarity. Among the colloids may be mentioned clay,'in a colloidal state, or slimes such as maybe obtained by decantasilicate. acacia, etc. Thus the colloidal constituents separated from the ore pulp as a preliminary operation as hereinbet'ore described.vor some l them, may, when votherwise sultable, be recovered from the colloidbearin'fg water of decantation7 or from the colloid-bearing froth, and after suitable purification or separation be themselves used as the colloidal agent for inhibitinp the flotation of certain of the mineral const-ituents of the ore pulp while permitt'vng the flotation of certain other of the mineral constituents.

ln the case of the Austinville ore one of the colloidal constituents of the ore recovered after preliminary separation as hereinbefore described has such a marked inhibitory action toward the 'flotation of Zinc sulfid that when added to a mixed concentrate of lead and Zinc sulfids obtained from this ore and the mixture subjected to froth flotation'V treatment in a Callow cell it permits the removal therefrom of high grade lead sulfid concentrate as the overflow froth. whilst inhibiting' the flotation ot' the major portion of the zinc sulid. which forms the' tailings pulp of the cell. despite the fact that the mixed concentrate was itself separated from the gangue by oil flotation. and that except for the additionof the inhibitory7 colloidY the lead and Zine sulfids seem to float with equal freedon'i. Colloidal precipitates may also in some lases be used. and thesemay be either separately formed and added to the pulp or they may be produced in the pulpvby adding thereto appropriate reagents. rllhus colloidal precipitates of barium sulphate. ferrie oxide (or hydrate). magnesium hydrate. calcium sulphate, various silicates. etc.. may be nia-de. by means Well understood. and used for the purpose of this invention.

i For the selection of the best inhibitory agent in a given case simple tests bascduipon the principles of general and colloid chemistry are sufficient, consideration being also l given to the questions of the relative amount of the various agents required. their cost and Igeneral suitability.

After the additiont. and intimate incorporation of the colloid. the ore pulp is then subjected to a flotation operation. which may be carried out in apparatus of the usual types. for example, in the Callow cell. or otherl well known flotation machines. and with the addition of a suitable oil or other flotation agent. which will further promote the desired selective flotation of certain of its mineral constituents or ingredients,

Thereafter. the remaining;- ore pulp may be subjected to a treatment which will effect the dispersion or deflocculation of the Colloids, if they are not 'already suffic'ently dispersed. so that they can be removedby decantation or they may be removed by the formation and removal of a colloid-bearing froth as hereinbefore described, and so that the ore pulp may then be again subjected to a flotation treatment for the recovery of certain other of its contained ingredients, this. second flotation operation being similarly carried out with the addition of an appropriate flotation agent and in an appropriate appara-tus.

For example. in the treatment of mixed lead-zinc sulfid Vores where the ore pulp is naturally relatively free from colloidal matter. `or has been freedv lof colloidal matter by the methods hereinbefore described,y there may be' added a small amount of a suitable colloid which will differentially inhibit the flotation ofy the zinc sulfid without interfering with the flotation of the lead sulfid. There may thus be added a small amtlunt of colloidal matter. where it is of proper col- 'loidal polar-typwhich has been separated from `ores carrying. an excess 'thereof7 the amount of the .flot-ati'on-inhibitory colloid being suflicientto bring about the desired inhibition of the flotation of the zinc. This amount can be readily determined for the particular ore bya few tests. lThe ore is then subjected to a flotation operation with the addition of a suitable flotation agent. for example. emulsified creosote oil, which will further promote the differential flotation of the lead sulfid.

The concentrateyas well as the tails, may be retreated in the usual manner, or the operation may be carried out in a series of flotation cellsr` as is common in the art.

After the separation of the lead concentrate. theore pulp is then subjected to a proper treatment for the removal of a part .or all of the added colloidal constituents.

and is then subjected to a further concentration by flotation for the recovery of zinc sulfid. rihe removal of the added colloidal mattei' is aocordingly'carried out to the extent required to promote the subsequent flotation of the Zine sullid. lhere the added colloidal constituents have become flocculated or adsorbed, they may be dispersed or deflocculated by the addition of a suitable dispensing' or deflocculatinp; agent Vor agents which will depend in kind and amount upon the so-callled colloidal polarity of the ingredients of the ore pulp and upon like considerations, l haye found small amounts of sodium silicate to be well adapted to promote this dispersitm with certain ores.

In other cases alkaline or acid agents may. be indicated. or salts of various kinds7 orpanic or inorganic, or agents which are themselves colloidal and which may he or- 1a-nic or inorganic. rThus l have successfully used aniongrothers. a cheap waste product of sugar manufacture known as l""foundry molasses,

tri-sodium phosphate, acacia (gum arabic), sulfuric. acid, caustic soda, etc.

Simple tests will serve to determine in any specific case what agent or agents can with advantage be employed to facilitate the delocculation or dispersion of the colloidal inhibitory agent. The major portion of the deflocculating agent will be carried out with the decanted colloid-bearing water and thc choice of agent will 'depend upon its effectiveness for the purpose and upon its cost, eect upon further treatment' of the pulp or water and upon like considerations.

The removal of the deflocculated colloidal constituents may be effected by a simple over-flow or decantation which may be carried out on the counter-'current principle, or it may be effected, with or without preliminary deiiocculation of the colloids, by the formation and removal of a colloid-bearing froth,.by means of suitable agentsand apparatus, as previously described. For the purpose of forming a froth selective for the colloid or colloids rather than for the metalliferous minerals, a variety of agents, organic and inorganic, are available. Simple tests will in any specific case be sufficient to determine the most suitable material, taking into consideration the relative cost, frothing power, colloid-selective power and'effeet upon the subsequent treatment of the mineral pulp and the colloid-bearing froth. l have successfully used various soaps, especially 'those containing rosin; oils having a relatively h igh pitch content, and even the well-known mineral 4selective frothing oils, when used in excess of whatl would be required for mineral froth flotation, and especially if preliminarily emulsilied, are in some cases colloid, rather than mineralselective. Other agents, such Vas 4certain salts, or even materials which arethemselves colloidal, may be used, and the greater part of the frothing agent will in general be removed from lthe pulp with the froth and colloids. The ore pulp, after suchfurther dilution as mayl be necessary, is then subjected to a further dotation treatment with the aid of a' suitable ilotation agent or agents, for example, emulsilied crude oil,

l pine oil and copper sulfate, and a zinc sulid concentrate thereby obtained. The concentrate and the tailings thus produced may be subjected to retreatment in a manner similar to that commonly practiced in the art.

ln the accompanyingv drawings, Figs. l, Q and 3 are diagrammatic How sheets illustrating, merely by way of example, three examples involving the application of the principles of the invention in the concentration of mixed ores 4and concentrates.

The :dow sheet of Fig. l illustrates the application of the invention `to the treatment colloid may be added to the ore during its preliminary treatment, as, for example, during the tine grinding, or may be added to the ore pulp that is ready for flotation. An appropria-te flotation agent, preferably select1ve with respect to the mineral A, is introduced into the ore pulp, which is then subjected to a flotation treatment. As the result of this flotation treatment there is obtained in the over-flow froth a concentrate of mineral A, which maybe retreated as desired. The tailings from the flotation treatment are then treated to remove the inhibiting colloid, as, for example, by' deflocculation followed by sedimentation of the granular portion of' the pulp and decantation of the vinhibitory-colloid bearing water, or by the formation and remo-val of aI colloidbearing froth, and are then subjected to a flotation treatment in the presence of an appropriate flotation agent. The resulting concentrate of the mineral 'B may be retreated as desired. c v

The flow sheet of Fig. 2 illustrates the treatment, in accordance with the principles of the present invention, of a mixed ore pulp containing naturally sufficient colloidal material to partially or Wholly inhibitthe flotation of one or more valuable minerals. As indicated by the flow sheet, this ore pulp is treated, as aforementioned, for the removal of substantially all of the inhibitory colloidal matter. The resulting pulp is then subjected to a flotation treatment in the presence of an appropriate flotation agent for obtaining a. mixed concentrate in which' the minerals A and B are present in approximately the same relative proportions to each other as in the'original ore. The minerals A and B are then separated by adding to the mixed concentrate pulp, with proper manipulation to secure intimate mixture, a colloid capable of inhibiting the flotation of mineral B and subject-ing the pulp to a flotation treatment whereb-y the mineral A is removed in the over-flow froth, and may be retreated as desired. The tailings from this differential flotation treatment are treat-ed for the removal of the inhibitory colloid and then subjected to a flotation treatment, in the presence of an appropriate flotation agent, thereby obtaining a concentrate of mineral B, which may be retreated as desired. `Where the tailings from this last dotation treatment are in the nature of middlings, they may be returned to ifieaeve the first flotation treatment, as indicated on ,of colloids as hereinbefore described. A colloid capable of inhibiting the flotation of mineral -B is added to the mixed concentrate pulp, intimately mixed therewith, and the pulp subjected to a flotation treatment,in the presence of an appropriate flotation agent preferably selective with respect to the mineral A. By this method the mineral A is removed in an overflow froth, leaving the mineral B, whose flotation has been inhibited, as the residue, which, except for its colloidal contamination, is itself a final concentrate. i

ln ore dressing, two alternative procedures are frequently possible; (l) to treat the entire tonnage of ore by a process having a certain cost per ton, and produce, thereby, tails clean enough to throw away, and concentrates good` enough to keep; or (2) to treat the entire tonnage by a still cheaper process yielding tails clean enough to throw away (and generally cleaner than those produced by the first alternative), and a small tonnage of low grade concentrate, which is..

then treated with more care -by a. process having a higher unit cost per ton, to yield the final concentrates. As will be readily seen, the total cost for either process is the sum of the constituent products of unit cost times tonnage treated.

ln the treatment of a zinc-lead-iron sulfid ore, with a dolomite gangue, such as oc curs at Austinville, Va., three separate col loid removals are involved. Briefly, this treatment comprises grinding all the ore, removing part of the colloid, and floating for 'lead,-and vthen removing more of the colloid and floating for zinc, and in addition to these Vtwo colloid removals, there is a preliminary removal to separate what `l call the primary colloid, that is, the clay mate- 'rial which is freein the ore before grinding.

This involves three separate decant-ation operations in which the full tonnage of ore is handled each time.

l'n accordance with the method illustrated bythe flow sheet of Fig. 2, l propose to re-.

move, with one or two decantations, as much of the colloid as is removed with the three decantat-ions mentioned in the "preceding paragraph, and todo this all before treating any of the pulpby flotation. The colloidfree pulp is then treated by flotation with appropriate reagents, so as to secure the cleanest possible tails,'which may be at once thrown away. The rough concentrate contains practically all of the lead and Zinc, a little gangue, and possibly some colloid.

This small tonnage of concentrate is then further treated, as indicated in the flow sheet of Figs. l or 2, depending upon how much gangue is carried over in the rough mixed concentrate, and .how much colloid it is necessary to add in order tosecure the separation of the minerals in the mixed concentrate.

It will, accordingly, be evident that by the method represented by the dow sheet of Fig. 2,*,the 'gangue is not only very cheaply eliminated, but is removed early in the concentrating process, so that in the subsequent operations only a relatively small tonnage of mixed concentrates have to be dealt with. ln this manner, processes can be employed for the separation ofthis mixed concentrate which would have so high a unit cost. as to be commercially prohibitive ifapplied to the original ore. Y

Throughout this 'specification and the appended claims, l intend to embrace, in the expressions colloids and colloidal constituents, both true colloids and those quasi or'borderland substances, which may not be truly colloidal but partake of the qualities of, or resemble, colloids, and without regard to the sources from which such colloidal matters'are derived. Thus, for the purposes of the present invention, the, colloidal con size upward ties of colloids, and are capable of existing in both the sol or gel state, or of being dispersed and coagulated, or flocculated and deflocculated, and exhibit flotation-inhibitory effects to an extent sufficient to justify their use in the process of the present invention.

l claim l. The method of effecting the differential flotation of minerals, which comprises adding to the mineral pulp a small amount of a colloid whichofi itself possesses the property of inhibiting the flotation of one `mineral species of the pulp while permitting the flotation of another mineral species, and subjecting the pulp to a flotation operation. 2. The method of elfecting the differential flotation of minerals, which comprises adding to the mineral pulp a small amount of a colloid inhibiting the flotation of certain mineral species of the pulp while permitting` the flotation vof another mineral species, subjecting the mineral pulp of a flotation operation, subsequently removlng from the remaining pulp the added colloid to an extent sufficient to promote the flotation of another mineral species of the pulp, and* subjecting the pulp to a further flotation operation.

3. The method vof effecting the differential reo ing to the mineral pulp a small amount of a colloid inhibiting the flotation of' certain mineral species of the pulp while permitting the flotation of another mineral species, subjecting the minei'al pulp to a flotation operation for the recovery of certain mineral species, adding to the remaining pulp an -agent promoting the dispersion of the added colloid, separating the dispersed colloid from the mineral pulp to an extent .Sufficient to promote flotation of other inineral species of the pulp, and subjecting the pulp to a further flotation operation for the recovery of such other mineral species.

4; The method of effecting the differential flotation of lead and zinc sulfids from minerals containin the same, which comprises adding to the mineral pulp a small amount of a colloid which of itself' possesses the propertj7 of .inhibiting the flotation of the Zinc sulfid While permitting the flotation of the leadsuld, subjecting the pulp to a flotation operation for the removal of the lead sulfid,

i' and subsequently subjecting the pulp to a further flotation operation for the removal of the zinc sulfid.

' 5. The method of effecting the differential separation of lead and 4zinc sulfids from min- Y erals containing the same, which comprises the lead sulfid, subjectingthe' pulp to a flota-A adding to the mine'ral pulp a small amount of a colloid inhibiting the flotation of the zinc siilfid while permitting the flotation of "l tion operation with the aid of a flotation agentpromoting the' flotation of the lead sul=d,.removin' from the remaining pulp the added colloid, to an extent suflicient to Y promote flotation of the zinc sulfid, and sibjectin, g' the pulp to a further flotation operation with the aid of' a flotation agent promoting the. flotation of the zinc snld.

6. The methodv of concentrating by flotation a mixed ore pulp containing different mineral `species and colloidal constituents, which comprises separating the colloidal constituents from the mineral pulp, subjecting the resultingl pulp to -a flotation treatment and. thereby obtaining a mixed concentra(A f the different mineral species, adding to the mixed concentrate pulp a small amount of a colloid-inhibiting the flotation of. certain of the mineral Vspecies Y of the concentrate While permitting the flotation of other mineral species, and subject-` ing the mineral pulp to a flotation operation.

' 7. The method of concentrating by flotation a mixed oi'e pulp containing different mineral species and colloidal constituents, ,which comprises separating the colloidal constituents from the mineral pulp, subjecting the resulting pulp Ato a flotation treatment and thereby obtaining a mixed concentrate of the different mineral species,

adding to the mixed concentrate pulp a small amount of.' a colloid inhibiting the flotation of certain of' the mineral species of the concentrate while permitting the flotation of other mineral species, subjecting the mineral pulp to a flotation operation and thereby obtaining a concentrate of the floatable mineral species, treating the tailings from the last mentioned flotation treatment for the removal therefrom of the aforementioned inhibitory colloid, and subjecting the resulting tailings pulp to a flotation operation thereby obtaining a concentrate of' the floatable mineral species.

8. The method of concentrating by Hotation a mixed ore pulp containing different mineral species and colloidal constituents, Which comprises separating the colloidal constituents from. the mineial pulp to an extent sufficient to promote flotation of the mineral species, subjecting the resulting pulp to a flotation treatment and thereby obtaining a mixed concentrate of the different Inineral species, adding to the mixed concentrate pulp a small amount of a colloid inhibiting the flotation of certain o,'f' the mineral species of' the concentrate ,fwhile permitting the flotation of other mineral species, subjecting the mineral pulp to a flotation operation and thereby obtaining a concentrate of certain mineral species, treating the residue from the last mentioned flotation treatment for the removal therefrom of the aforementioned inhibitory colloid, and subjecting the colloid freed residue to a flotation treatment and therebyv obtaining a concentrate of another mineral species.

9. The method of concentrating` a mixed ore pulp containing different mineral species and colloidal constituents, which comprises separating the colloidal constituents from the mineral pulp, adding to the mineral pulp a small amount of a colloid inhibiting the flotation of certain mineral species While permitting the flotation ,of other mineral species, and subjecting the mineral pulp to a flotation operation.

l0. The method ofl concentrating by flotation a mixed ore pulp containing different mineral species and colloidal constituents, which comprises adding to the pulp a deflocculating agent for effecting the deocculation of the colloidal constituents` separating the deflocculated colloidals from the pulp` subjecting the pulp to a flotation treatment and thereby obtaining a mixed concentrate ofthe different mineral species. adding to the mixed concentrate pulp a small amount of a colloid inhibiting the flotation of certain mineral species there ioo thereby obtaining a froth product containing certain mineral species and a residue containing certain other mineralspecies.

11. The method of concentrating by flotation a mixed ore pulp containing different mineral species vand colloidal constituents, which comprises separating the colloidal constituents from the pulp, subjecting the pulp to a flotation treatment and thereby obtaining a mixed concentrate of said different mineral species, adding to the concentrate pulp a small amount of a colloid inhibiting Athe flotation of certain of the mineral species thereof While permitting the flotation of other mineral species, subjecting the concentrate pulpy to a flotation operation andthereby obtaining a concentrate of one vof the mineral species contained in said ore` residual pulp of the last mentioned flotation operation an agent promoting the dispersion of the colloids contained therein, removing the dispersed colloids *from said residual pulp, and subjecting said residual Ipulp to a flotation/ operation and thereby obtaining a concentrate of another ymineral species contained in said ore pulp.

12. The method o'f concentrating by flotation a mixed ore pulp containingA different mineral species and colloidal constituents, Which comprises separating the colloidal constituents from the pulp, subjecting the pulp to a flotation treatment and thereby obtaining a mixed concentrate of said different mineral species, adding to the concentrate pulp a small amount of a colloid inhibiting the flotation of certain mineral species thereof While permitting the flotation of other mineral species, subjecting the concentrate pulp to a flotation operation and thereby obtaining a' concentrate of one mineral species contained in said ,ore pulp, subjecting the residual pulp of the last mentioned flotation operation to appropriate' treatment for dispersing said added inhibitory colloid, removing the dispersed colloid from said residual pulp, and subjecting said residual pulp to a flotation operation and thereby obtaining a concentrate of another mineral species contained in said ore pulp.

13. The method of effecting the differentialv flotation of different mineral species contained in a. mixed ore pulp, which com prises adding to the pulp a small amount of a colloid inhibiting the flotationof a cer tain mineral species thereof while permit ting the flotation of another mineral species thereof, subjecting the pulp to a flotation operation for the recovery therefrom of a certain mineral species, subjecting the. re-

maining pulp to appropriate treatmentn for ldispersing said added inhibitory colloid and then removing the'dispersed colloid from the pulp to an extent sufficient to promote flotation of another mineral specles of the pulp, adding to the mineral species and colloidal constituents.A

which comprises separating the colloidal constituents from the pulp to an extent suf fcient to promote flotation of the mineral species contained therein, subjecting the thus colloid-freed pulp to a flotation treatment and thereby obtaining a -mixed concentrate of the different mineral species, adding to the mixed concentrate pulp a small amount of a colloid inhibiting the flotation of a certain mineral species thereof While permitting the flotation of another mineral species thereof, subjecting the pulp to a flotation operation and thereby obtaining a concentrate of said certain mineral species, subjecting the residual pulp from the last-mentioned flotation treatment to ap ropriate treatment for dispersing said added inhibitory colloid and then removing the dispersed colloid from the pulp to the extent required to promote flotation of another'mineral species of the pulp, and subjecting the thus `colloid-freed pulp to a flotation treatment and thereby obtaining a concentrate of said other mineral species.

l5. The method of effecting the differential flotation ofdifferent mineral species in a` mixed ore pulp which comprises adding to the pulp a small amount of a colloid in hibiting the flotation of a certain mineral species thereof While permitting the flotation of another mineral species thereof, subjecting the mineral pulp to a flotation operation for the recovery of said certain mineral Species, subsequently removing the said added inhibitory colloid in a dispersed condition from the'remaining pulp to the extent required to promote the flotation of another mineral lspecies of the pulp, and subjecting the'pulp to a further flotation operation for the recovery of said other mineral species thereof.

. 16. The' method of concentrating by flo- 7 tation 'a mixed ore pulp containing different mineral species. which comprises subjecting the ore pulp to a flotation treatment and thereby'obtaining a mixed concentrate vof the different mineral species, addingto the mixed concentrate pulp a small amount of a colloid which of itself possesses the property of inhibiting the flotation of certain mineral species thereof, While permitting the flot-ation of other mineral species, and subjecting the mineral pulp to a flotation operation and thereby obtaininga froth product containing certain mineral species and a residue containing certain other mineral species.

In testimony whereof I affix my signature.

WALTER o. BoRoHERD'r, 

